The composition of many Australian woodland and forest bird assemblages is controlled by a single, hyper-aggressive native bird, the noisy miner Manorina melanocephala. In many situations at least 80% of small bird species are excluded from otherwise suitable habitat by noisy miners, and this exclusion results in a shift from an assemblage with diverse foraging strategies to a homogenized one, predictably dominated by large-bodied and ground-foraging species, and a high proportion of avian predators of vertebrates. The cascading ecological effects of this shift are likely to be substantial. Yet while numerous individual, local-scale studies have documented this phenomenon, and large datasets exist, there remain significant knowledge gaps. Despite the critical importance of this issue to the health of woodland bird assemblages across eastern Australia, we lack a large-scale synthesis of the nature, causes and solutions to the noisy miner problem.

This working group will address these knowledge gaps by harnessing diverse existing datasets and using them to develop and test models of noisy miner occupancy and impacts, leading to new management approaches. Collectively, working group members possess significant avifauna datasets representing decades of research from across the range of the noisy miner, in many ecosystem types, and in urban, periurban, and rural areas. These datasets will be standardised and analysed in order to, firstly, reveal geographic variation in the effects of noisy miners on bird assemblages; secondly, develop alternative conceptual models of the anthropogenic and natural factors contributing to noisy miner domination; and thirdly, test the models using the combined data set in order to identify a single unified theoretical model of the process of noisy miner invasion. Finally, we will develop a decision support tool for management responses to noisy miners which identifies where action to control noisy miner impacts is necessary, and which approach is most cost-effective.

For further enquiries about this group please contact the Principal Investigator,
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The first meeting of the working group was held at Indooroopilly golf links, an appropriately noisy miner-infested location. Most of the participants already knew one another, and for years many had been suggesting that such a workshop ought to be held to nut out why different patterns of noisy miner occupancy and impact seemed to emerge in different systems, and bring together evidence on alternative management approaches. Workshop 1 aimed to start the process of tackling the first of these questions. Throughout the first day, presentations from all participants established that collectively, we had data and experience with noisy miners covering much of eastern Australia, from central Queensland to Tasmania, from urban to agricultural and forest landscapes, and in many different ecosystems. Key data gaps were identified in southern NSW and Queensland north of the Carnarvon Range.

Several common themes emerged from the presentations and the discussions that they precipitated. The substantial negative impact of noisy miners on almost all small birds was considered well-supported, and there was evidence of an increase in their density. They were clearly associated with woodlands and open forests of eucalypts and allied genera, but also brigalow (an Acacia). Soil fertility, rainfall and habitat structure were considered to be important.

The working group decided to develop two conceptual models: 1) A model of the probability of a given site being part of an Interspecific Exclusion Zone – that part of a noisy miner territory from which smaller species are reliably excluded; and 2) A model of noisy miner impact on small birds. The first of these was developed during the workshop, and linked environmental factors to the IEZ, mainly through their influence on: 1) availability and reliability of food resources, and 2) territory defensibility. Ralph and Jim demonstrated an approach suitable for evaluating and estimating the parameters of a formalised version of our conceptual model. The afternoon was spent identifying potential quantifiable proxies for the nodes in our conceptual diagram.

Before wrapping up the workshop, we heard updates on Key Threatening Process nominations and on the current state of the policy and management response to noisy miners, and commenced planning for two papers: 1) a review and presentation of the conceptual models; and 2) presentation of the formal modelling process and findings. The group divided up the large amount of work to be done before Workshop 2, which will focus on noisy miner management.

The second workshop focussed on reviewing the work done since Workshop 1, and synthesising knowledge about the cost effectiveness and appropriateness of management responses to the Noisy Miner issue, as well as approaches for communicating the group’s findings. The conceptual model of noisy miner impact was discussed and refined, and the structure of the first manuscript, which presents the two conceptual models, was re-worked, and preliminary results of the large-scale modelling of noisy miner abundance were presented and discussed. As the National Threatened Species Scientific Committee is currently considering a nomination for noisy miners as a Key Threatening Process, we scheduled a phone linkup with John Woinarski of the Committee and DSEWPaC staff. The pros and cons of adding each of bell and yellow-throated miners to the NM listing nomination were discussed, and the Working Group concluded that the KTP should continue to be focussed on noisy miners.

The group started work on developing a set of management recommendations. We agreed on the following as the overall aim of management: “Reduce the impact of Noisy Miners to deliver measurable benefits to local populations and assemblages of birds of conservation concern”. As the most controversial potential management action was direct management of miners (culling), the group developed a set of conditions under which direct management may be acceptable at a site. An outline for a third manuscript was developed, which will incorporate both an evaluation of management effectiveness for possible responses to NM problem and a cost effectiveness analysis of a subset of alternative actions, plus a set of recommendations.

To broaden our awareness of the challenges of managing overabundant native species, we held telephone and Skype link-ups with Prof Scott Robinson, Department of Natural History, University of Florida and Prof Steve Rothstein, Department of Ecology, Evolution and Marine Biology, University of California (Santa Barbara). In a scenario similar to the Noisy Miner in Australia, the Brown-headed Cowbird has benefitted from fragmentation of North American temperate forests and an increase in pastureland. The presence of this brood parasite in forest remnants is contributing to the decline of endangered and threatened American songbird populations. Scott and Steve provided their perspective on what we can learn from the experience of management of cowbirds in the US. It was clear that a well-functioning expert advisory group was an important part of the success of control strategies, and the ACEAS working group agreed to evolve into an independent advisory group on Manorina management post-ACEAS. Finally, the group considered the challenges of communicating the potentially unpalatable message that a native species needed to be managed for reduced abundance. The group identified the major target audiences and the concerns each were likely to have that needed to be addressed.

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